1. Field of the Invention
The present invention generally relates to a tablet and, more particularly, to a divisible pharmaceutical tablet.
2. Description of the Prior Art
The divisible pharmaceutical tablet is not a new and recent development and has long been well known. The divisible pharmaceutical tablet has defined therein at least one score along which the tablet is divided into two tablet pieces by the application of a finger pressure. For example, the Japanese Laid-open Patent Publication No. 61-289027, published Dec. 19, 1986, (which in turn corresponds to the published European Patent No. A1-207,888, published Jan. 7, 1987), discloses a pharmaceutical tablet of a round shape having flat surfaces opposite to each other and also having at least one diametrically extending, generally V-sectioned score defined on at least one of the surfaces thereof. The surface of the round tablet where the V-sectioned score is defined has a pair of surface regions that are inclined inwardly from the circumferential tablet edge at an obtuse angle, for example, about 170 to 150 degrees, with respect to each other, each of said surface regions being inclined at an angle of about 5 to 15 degrees relative to the plane of the cross section of the tablet.
The round pharmaceutical tablet disclosed in the Japanese publication No. 61-289027 or European publication No. A1-207,888 is also featured in that the circumferential tablet edges opposite to each other are chamfered at an angle of about 20 to 40 degrees with respect to the plane of the cross section and that the V-sectioned score has an acute angle of, for example, 90 degrees and also has a depth generally equal to that of the chamfered circumferential tablet edge while the bottom of said V-sectioned score occupies a position no more than one third of the total depth of the tablet at the middle.
This prior art pharmaceutical tablet is indeed easy to divide when, while the tablet is placed on a support surface, for example, a table or a palm of a hand, with the V-sectioned score facing towards the support surface, an external pressure is applied to a center area of the tablet so as to act in a direction close towards the support surface. However, there may be a problem when the external pressure is applied in the wrong way, i.e., in a direction diagonally with respect to the plane of the cross section of the tablet. Once the external pressure is applied in the wrong way, a portion of the circumferential tablet edge may undesirably break or shatter, resulting in the tablet pieces of different size and, hence, dosage when the tablet is eventually divided along the V-sectioned score.
Japanese Laid-open Utility Model Publication No. 2-14333, published Jan. 29, 1990, discloses a pharmaceutical tablet having a right-angled peripheral edge on opposite surfaces thereof and also having a generally V-sectioned score defined on the opposite surfaces thereof in alignment with each other so as to leave symmetrical tablet pieces on respective sides of the V-sectioned score. The tablet disclosed therein is of a shape corresponding to the shape represented by two oval shapes adjoining to each other and also of a generally annular shape.
The second mentioned prior art pharmaceutical tablet is also easy to divide with no possibility of a portion of the peripheral tablet edge breaking or shattering even though the external pressure is diagonally applied. However, it appears that a portion of any of the peripheral tablet edges is susceptible to breakage under the influence of impacts which may be induced during transportation or storage of a batch of the pharmaceutical tablets. Once this occurs, the division of the pharmaceutical tablet results in the tablet pieces of different size and, hence, dosage, as is the case with the first mentioned prior art pharmaceutical tablet.